strike zone

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun The area over home plate through which a pitch must pass to be called a strike, roughly between the batter's armpits and knees.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Baseball) the area above home plate where, if a pitched ball passes through and is not hit by the batter, the pitch counts as a strike. Specifically, it is directly above home plate and at a height from the knees to the shoulders of the batter.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun baseball The area through which if a pitched ball passes, it will be called a strike, typically from the batter's knees to the belt and the width of home plate.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun (baseball) the area over home plate between a batter's knees and shoulders through which a pitch must pass in order to be called a strike